Activated carbons are used in the treatment of water or aqueous solutions as adsorbents to remove impurities or adjust the concentration of dissolved components.
Among such activated carbons, zinc chloride-activated carbons having many mesospores are commonly used, in particular, to remove the coloring of the liquid phase of an aqueous solution, etc.
Although zinc chloride-activated carbons can effectively remove coloring components, wood powder is used as their raw material, and they are generally provided as powdered activated carbons; thus, these activated carbons are not suitable for column treatment or heat regeneration of used activated carbons. Further, granular products can be obtained by sieving; however, the granular products have a low hardness, causing problems in that they are difficult to handle during transport and loading, and in that powdering and fine granulation occur during use.
Moreover, as for chemical-activated carbons, the firing temperature during the manufacture thereof is low; therefore, many surface oxides are present on the surface of the activated carbons, which problematically reduces the adsorption of trace organics in solutions, and low-molecular-weight molecules, such as iodine.
In order to solve the above problems of zinc chloride-activated carbons, PTL 1 discloses a method for producing a chemical agent-activated molded active carbon, wherein a mixture of an active carbon raw material capable of being activated by a chemical agent and an activating chemical agent (e.g., zinc chloride) having a water content of 25 wt. % or less and an active component content of 60 wt. % or more is heated by a general method to form a reaction product, and the reaction product is molded, baked, washed, and dried to obtain a molded active carbon.
Furthermore, as a method for manufacturing an activated carbon having many mesopores, PTL 2 discloses an activated carbon for highly treating clean water obtained by mixing 100 parts by weight of carbonaceous raw material with 0.2 to 1.5 parts by weight (in terms of calcium) of at least one calcium compound, and carbonizing and activating the mixture; and also discloses a method for manufacturing the same.